First, select a grocery cart that rolls straight and smooth. Your first exercise is to learn to drive the cart with only your fingers on the far outer ends of the handle. Using the thumb and forefinger only lets you feel the handling changes we will be making.
Swing over to the beverage department and pick up three 12-packs of canned drinks. The placement of these will be the adjustments used to change the handling. Next, find a short island, preferably not in the busiest area of the store. Here you can take as many laps as you need to complete your lessons.
Begin by placing all three "weights" across the front of the cart. Walk briskly, but don't run. Begin your approach toward the end of the straight by positioning your cart in the middle of the aisle. Start your turn by pulling on the left corner and pushing on the right. You will find the cart has a push. The front will not want to turn the corner.
When you slow down, you will need to push the handle to the right. Now, your control will be more effective. Finally, the front will begin to turn while the lightly loaded rear will easily slide sideways. Accelerating out of the corner, the rear will be loose. Meaning, if you continue pushing hard while finishing the turn, the cart will spin out.
What you have encountered is the classic push-in/loose-out syndrome. The car has a push and goes to the outer edge of the track. It slows, the front catches, the rear comes around and the car drives down across the track. Beginning drivers often misdiagnose this condition as being loose.
Moving the weights to the rear has a somewhat opposite effect. Your fingers will have good leverage over the light front end. At the end of your straight, it will be easy to make the cart turn left. However, on corner exit, when you pick up some speed and try to maintain the turn, there will be a different situation. At this point, the cart will be trying to make the turn wider, perhaps wider than the aisle unless you slow down. This is called a "push on corner exit." On a real race car, rear tire stagger (larger right rear) can often cure the problem.
Next, move the three weights to the center of the left side of the cart. This will result in the corner entry and exit being controllable while still carrying a good speed. This is the ideal cornering handling situation. It is seldom achieved consistently under racing conditions.
Try moving the weights to the right side while still making your left corners. When the cart feels like tipping over you will understand why left-side weight makes a car fast.
Though these examples of handling may be exaggerated, you can get the feel of what a race car driver experiences.